Year	Number
1970	19.65833
1971	20.64567
1972	20.80714
1973	20.77273
1974	21.83815
1975	21.34463
1978	19.09917
1979	17.85764
1993	12.39592
1994	12.25892
1995	12.56118
1996	13.2061
1998	14.46306
1999	14.14456
2000	14.57746
2001	14.31238
2002	13.1973
2003	13.67563
2004	13.49492
2005	14.43294
2006	13.21017
2007	13.9915
2008	14.46252
2009	13.12919
2010	12.76014
2011	11.79602
2012	12.8595
2013	12.36134
2014	13.23091
2015	11.98379
2016	11.6348
2017	11.5937
2018	10.7789